1. Field of the Invention
The present invention relates to a vibrating mirror element, a distance measuring apparatus, and a projector, and more particularly, it relates to a vibrating mirror element, a distance measuring apparatus, and a projector each including a resonant drive portion and a drive control portion controlling the driving of the resonant drive portion.
2. Description of the Background Art
A vibrating mirror element, a distance measuring apparatus, and a projector each including a resonant drive portion and a drive control portion controlling the driving of the resonant drive portion are known in general, as disclosed in Japanese Patent Laying-Open No. 2008-009446.
Japanese Patent Laying-Open No. 2008-009446 discloses an image-forming apparatus having a resonance type light-deflector (vibrating mirror element) for deflecting a laser light, a driving portion (resonant drive portion) for oscillating a first movable element (mirror portion) around an oscillating axis, a driving portion (correction drive portion) for oscillating a second movable element around an oscillating axis, and a driving control portion (drive control portion) for controlling the driving portions. In the resonance type light-deflector of this image-forming apparatus according to Japanese Patent Laying-Open No. 2008-009446, the driving control portion is configured to control the driving portions (the resonant drive portion and the correction drive portion) to oscillate a plurality of movable elements and a system constituted by torsion springs simultaneously at a reference frequency and a frequency of an even multiple of the reference frequency. Thus, the first movable element is configured such that the turning angle velocity is substantially constant during a prescribed period of time in one cycle of the oscillation.
In the resonance type light-deflector disclosed in Japanese Patent Laying-Open No. 2008-009446, however, the period of time when the turning angle velocity of the first movable element can be substantially constant is disadvantageously limited whereas the first movable element is configured such that the turning angle velocity is substantially constant during the prescribed period of time in one cycle of the oscillation.